Description: F. stainesii is a simple or clumping
barrel/column cactus with thick red spines. In habitat plants must be a
great age, often forming into quite massive groups,
with several subsidiary barrels growing from the main one, with deep
green bodies densely covered with bright red spines up its entire
length. Most plants have bright red spines with bristlelike, white
radials—a wonderful contrast, but in some populations the white bristles
are occasionally absent. Such variation has led to establishment of
several names for this species.
Columnar deep green up to 2.4(-3) m tall and 30 t0 40 cm in diameter,
with several subsidiary barrels growing from the main one.
Ribs: 13-20, compressed, more or less ondulate.
Areoles: Distant to closely set and almost contiguous in older
Radial spines: Sometime absent or usually reduced to long white
or straw coloured hairs on the areoles that appears later with age.
spines: Several, subulate-acicular, stright or slightly curved, more
or less flattened and angular at first bright red/purplish becoming dull
yellow with age, but some populations also boast
yellow-spined individuals, and the white bristles are occasionally
Flowers: Yellow to red, about 2,5 cm long, scales on the ovary
numerose, orbicular, imbricated, inner perianth segment oblanceolate,
obtuse or apiculate.
Fruit: Yellow, somewhat succulent, dehishing by basal pore, 3 to
4 cm long, crowned by persisting perianth.
Seeds:1,5 mm long, brownish, pitted with a small basal hilum.
Two subspecies are recognized:
'pilosus' with additional wispy and hairy white spines
also known as Ferocactus pilosus. It appears also to
have brighter red, bigger and thicker central spines compared to more
only red acicular spines and none (or very few) hairy white spines.
However this two
'subspecies' look very similar and are linked one to each others by
populations of plants with intermediate characteristics. Nowadays both
are thought to belong to a unique polymorphic species with some
individual covered in fine white hairs, while others do not.